Conventionally known is the following transmission. In the transmission, a rotational output (rotational power) of an engine is converted into electric power by a generator. The electric power resulting from the conversion is converted into rotational power by a motor. The rotational power resulting from the conversion is supplied to a rotating mechanism.
For example, Japanese Patent Application Laid-Open No. 2002-345109 (“JPA'109”) shows a vehicle. The vehicle shown in JPA'109 is a hybrid vehicle. This vehicle includes an engine, an accelerator pedal, a first rotary electric machine, a second rotary electric machine, and a drive wheel. The first rotary electric machine is coupled to an output shaft of the engine. The first rotary electric machine functions mainly as a generator. The second rotary electric machine is electrically connected to the first rotary electric machine. The second rotary electric machine functions mainly as a motor. A set of the first and second rotary electric machines is used as a transmission machine. By a current flowing in the first rotary electric machine and the second rotary electric machine, power running is performed. The second rotary electric machine is coupled to the drive wheel of the vehicle.
In the vehicle as shown in JPA'109, a depression of the accelerator pedal depressed by a driver represents a request for acceleration of the vehicle. The vehicle as shown in JPA'109 is, if provided with an electronic-controlled throttle device, able to optionally adjust the amount of air taken in by the engine. The vehicle is, therefore, controlled in the following manner, for example. A target output of the second rotary electric machine (motor) is determined based on the vehicle speed and the amount of depression of the accelerator pedal depressed by the driver. A target electric power to be generated by the first rotary electric machine (generator) is determined in accordance with the target output of the second rotary electric machine. A target output of the engine is determined in accordance with the target electric power to be generated. The amount of air taken in and the amount of fuel injected by the engine are controlled so as to achieve the target output. In this control, the first rotary electric machine is controlled in its generating electric power and the second rotary electric machine is controlled in its output. In a case where the vehicle as shown in JPA'109 is configured with its accelerator pedal mechanically coupled with its engine throttle, the electric power generated by the first rotary electric machine and the output of the second rotary electric machine are controlled in accordance with an actual output of the engine. In JPA'109, as described above, electric power (output) of the rotary electric machine is controlled so as to allow applications to various types of vehicles with different characteristics.